1. Field of the Invention
The present invention relates to a rod plate for a cervical vertebra which connects and bonds a cranium portion and a cervical vertebra portion, and a connector for connecting them. More particularly, the present invention relates to a rod plate for a cervical vertebra which can easily mount to the cranium portion, and a connector which can set a mounting angle of the rod plate for the cervical vertebra and an implant to a desired angle.
2. Description of the Related Art
As a structure of a connector for a rod plate and a structure of the rod plate according to the related art, there are structures shown in FIGS. 1, 2 and 3.
At first, the related art concerning the connector portion will be described with reference to FIGS. 1 and 2. The structure is made such that a flat portion 5 is provided in a head portion of a screw portion 3 screwed and inserted as an implant screwed and inserted to a body of vertebra in a vertebral bone, and a U-shaped groove 7 is provided in the flat portion.
Then, a connector 11 for connecting a bone connecting rod 9, for example, connecting a vertebral bone and a vertebral bone and the implant 1 described above is provided with a connector main body 15 having an oblong through hole 13 freely inserting through the rod 9. A protruding portion 17 freely engaged with and disengaged from the U-shaped groove 7 of the implant 1 is provided in the connector main body 15, and a semicolumnar engaging portion 19 which is slightly longer in the same direction as a penetrating direction of the through hole 13 is provided at a front end of the protruding portion 17.
A rectangular portion 21 is formed in a side of the protruding portion 17 of the connector main body 15, and an annular lock member 23 is slidably fitted and supported to the rectangular portion 21. A lot of radial grooves are formed on a contact surface on which the lock member 23 is brought into contact with the flat portion 5 in the implant 1, around an axis of the protruding portion 17, whereby a concavo-convex surface 25 is formed, and a contact surface 5a of the flat portion 5 in the implant 1 is formed in the similar concavo-convex surface.
In order to fasten and fix the rod 9 inserted to the through hole 13, a screw hole 31 freely screwing a fastening screw 27 is provided in the connector main body 15. The screw hole 31 is formed in an inclined manner with respect to the through hole 13 in such a manner as to press the rod 9 in a direction of the lock member 23 by the front end portion of the screwed fastening screw 27.
Accordingly, when engaging the protruding portion 17 of the connector main body 15 with the U-shaped groove 7 of the implant 1, positioning the flat portion 5 of the implant 1 between the engaging portion 19 and the lock member 23, inserting the rod 9 to the through hole 13 and thereafter fastening the fastening screw 27, the rod 9 is moved in the direction of the lock member 23 by the front end portion of the fastening screw 27, the concavo-concave surface 25 of the lock member 23 is brought into contact with the contact surface 5a of the flat portion 5 in the implant 1 and the concave-convex surfaces are engaged with each other, so that it is possible to fix the rod 9 to the implant 1.
Next, the related art of the rod plate for the cervical vertebra connected to the above connector will be described with reference to FIG. 3.
A fixing device 86 is structured such as to be provided with a mounting portion 81 to a cranium portion 85 and a mounting portion 83 to a cervical vertebra 82, the mounting portion 83 to the cervical vertebra 82 is formed in a rod shape, and the mounting portion 81 to the cranium portion 85 is formed in a flat shape. Further, the flat mounting portion 81 is suitably bent with respect to the rod-shaped mounting portion 83 and is bent in a circular arc shape so as to be asymmetrical.
The rod-shaped mounting portion 83 is integrally supported and fixed to a supporting and fixing device 84 suitably mounted to the cervical vertebra 82, and is integrally fixed to the flat-shaped mounting portion 81 in the cranium 85 by inserting the screw 80 to the mounting hole provided in the mounting portion 81 and screwing to the cranium 85.
In the connector structure as described above, since the structure is made such as to press the lock member 23 via the rod 9, it is impossible to stably mount the connector main body 15 to the implant 1 in a state that the rod 9 is not inserted to the through hole 13 of the connector main body 15, so that there is a problem that it is hard to set the connector.
Moreover, in the structure of the rod plate connected to the connector described above, since the shapes are different between right and left, it is necessary to properly use the right and left parts and it is necessary to independently manufacture them, so that it is hard to manufacture them. Further, there is a problem that it is not easy to align the longitudinal direction of the rod-shaped mounting portion with the supporting and fixing device.